edd at debian.org
Sat Apr 2 05:38:20 CEST 2011
On 1 April 2011 at 11:15, Davor Cubranic wrote:
| On 2011-03-31, at 8:12 PM, Sean Robert McGuffee wrote:
| > Thanks for the info about modularity. I'll definitely be wikipedia'ing that.
| > Also, thanks for clarifying the package author thing--I literally was
| > imagining some sort of function that writes something related to packages.
| You know, I can see that, esp. in the context of the rest of that section. I'll send a suggestion to the manual maintainers to consider using a clearer expression.
Thanks for doing that on r-devel! Much appreciated.
| > In particular with useDynLib, what type of argument(s) go(es) in it?
| > For example, do I literally copy a file object into it somehow?
| What I have in my NAMESPACEs, and is used in the example in section 1.6.4 of the manual, is just the name of the DLL without the extension. And it's a symbol, rather than a string, so no quotes.
| > For example, say I want to link against libpng14.
| > On the machine I'm sitting at, it's located at:
| > /usr/local/lib/libpng14.a
| > How would I use useDynLib in that case?
| Aha, you may not need to dive into "useDynLib"s dark corners after all. I only use "useDynLib" to link to my package's own library. For linking to a library provided by another package, such as Rcpp or a system library, I have a src/Makevars in my package that sets the right "-l" compiler switches and assigns them to PKG_LIBS variable. See section "1.2.1 Using Makevars" in R-exts. It goes into way more detail than you'll need (ignore all stuff about "configure" for now), or see how Rcpp.package.skeleton creates a Makevars file that has all the switches to link against Rcpp's DLL. (In their case it's a bit more general, and you may really need nothing more than "PKG_LIBS=-lpng14".)
I think this is the second this has come up so I really do need to add an
example in the Rcpp-package vignette and maybe also the Rcpp-FAQ.
| I admit I approach this on a need-to-know basis myself, IOW only about as far as I need to make my code work. But it does work, and I have also seen it used in a number of packages I've looked at, so I don't think it's too far off the mark. Others on the list can chime in if I'm grossly misrepresenting the linking mechanism or what you should do in your case.
Indeed: 'Need-to-know' works pretty well. R is so bloody rich and featureful
than you can't possibly know everything at the same depth.
That said, one should read the manuals, and possibly a few times over (and R
Core does add things there, so a 'ChangeLog' for each manual would be nice).
But there are always lots of examples on CRAN one can follow...
Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
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